CD polymer

CD polymers (CDPs) are macromolecule derivatives which carry multiple CD units. These units are appended by chemical bonding or physical mixed method. These kinds of polymers not only have the better ability of identification and encapsulation, but also possess good mechanical strength, stability and chemical tenability. The comprehensive function of CD cavity and polymer network could improve the properties of materials. The early investigations always focused on the formation of CDPs by monomers copolymerization. However, several papers showed that the CDs could link to the natural macromolecules to form novel polymers. These polymers were expected to be applied in the functional materials, separation and analysis technology, biomedical engineering, environmental and other high-tech fields [17]. 

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Kaur, I.P., et al. 2004. Development of topically effective formulations of acetazolamide using HP-(3-CD-polymer co-complexes. Curr Drug Deliv 1 65. 

Gonzalez and coworkers synthesized a series of polyamidine-CD polymers via AABB-type condensation of diamino-CD or di(2-aminoethanethio)-CD monomers... 

Adsorption chromatography on cellulose was examined for azo dyes that form complexes with CDs using aqueous solutions of a-CD as eluents. The cyclodextrin substantially increases the RF values [61], Commercial a-, [>-. and y-CD polymers were used for the same purpose, however changes of RF were observed only for some azo dyes [62], 2-Hydroxypropyl-P-cyclodextrin used in 10-20% concentration causes complete elution of many compounds [63],... 

Table III. Association constant and solubility enhancement of "monofunctional" and "bifunctional" guests with CD and soluble CD polymer...

Table IV. Separation of some Indole alkaloids on p-CD polymer...

Transferrin-containing CD polymer-based nanoparticles were studied as nucleic acid delivery system that can be modified for targeted delivery of small interfering ribonucleic acid (siRNA) to cancer cells. Molecular studies showed that the siRNA CD nanoparticles reduced levels of Ewing s transcript by 80% and inhibited growth of cultured Ewing s tumor cell line. It was also reported that this delivery system indicated a lack of toxicity [39],... 

The presence of P-cyclodextrin grafts allows the formation of smaller emulsion droplets in comparison to systems formed using silicone oil. Thus, the diameters of PMHS-CD droplets were smaller than the silicone oil droplets by a factor of 2. The presence of substituents containing ester groups (20 ester groups per graft) makes the PMHS-CD polymers more polar than silicone oil. The backbone of PMHS-CD... 

Some non-oxide nanoparticles such as PbS and CdS can be used to prepare polymer-inorganic nanocomposites by a double-microemulsion process [103]. In this case, two precursor micro emulsions must be prepared separately first and then mixed together for polymerization. Using CdS-polymer nanocom-... 

CD polymers can be synthesized (1) by radical polymerization of monofunctional CD monomers, (2) by polymer-analogous reaction of polymers with CDs, and (3) by partial crosslinking of CDs, as exemplified below. 

Crosslinking of a-CD with epichlorohydrin in aqueous solution under well controlled conditions furnished hyperbranched water-soluble a-CD polymers [96,97]. On the other hand, template directed crosslinking of a-CD, threaded on PEG, gave rise to linear CD polymers with two to three bridges between every two neighboring rings, or so-called molecular tubes, as shown in Fig. 2 [98-101],... 

Table 7 Comparison of binding potentials of 3-CD, (3-CD dimers and a 3-CD polymer...

The interaction of CD dimers or CD polymers with side chain guest polymers leads to the reversible formation of three-dimensional supramolecular networks, as shown in Fig. 17. 

Fig. 17 Formation of supramolecular networks from CD polymers and guest...

A remarkably different system comprised of a P-CD polymer and a guest polymer was recently described by Gref et al. [209], They mixed aqueous solutions of neutral P-CD epichlorohydrin polymer and a neutral lauryl ester of dextran, both of high molecular weights, and received no macroscopic gels but well-defined and... 

Fig. 18 Viscosities of mixtures of a 3-CD polymer (P-cyclodextrinyl-PIBMA) and a guest polymer (tert-butyl anilide of PIBMA) as functions of the molar fraction of guest groups in water for different shear rates D (s-1) of 66 (filled diamonds), 131 (filled squares), 196 (filled circles), 393 (open triangles), and 590 (open circles) at constant total polymer concentration of 2 wt% [202]...

The free radical polymerization of complexed monomer 19a was carried out at different temperatures in water in the presence of 1 mol% water-soluble azoinitiator. The temperature range of interest was 50-90°C, to determine vo below and above the 7)m of 65°C of the given CD-polymer system (P21a). 

Fluorescent naphthol-based polymers were prepared by HRP-catalyzed polymerization of 2-naphthol in AOT/isooctane reverse micelles to give the polymer microspheres.31 The precipitated polymer was soluble in a range of polar and nonpolar organic solvents and possessed quinonoid structure. The reverse micellar system induced the peroxidase-catalyzed copolymerization of p-hydroxythiophenol and />ethylphenol, yielding the thiol-containing polyphenol particles.32 The attachment of CdS to the particles gave the CdS—polymer nanocomposite showing fluorescence characteristics. 

Amiel et al. [85, 86] investigated the formation of ternary complexes of a water soluble epichlorohydrin-linked f-CD polymer, cationic surfactant dodecyltrimethy-lammonium bromide (DTAB), and a polyanion sodium salt dextran sulfate (NaDxS) by viscometry and small angle neutron scattering. They proposed a structure of polyion complexes between NaDxS and the supramolecular polycation formed from fi-CD polymer and DTAB. More recently, Amiel et al. [87] have characterized in detail the supramolecular polycation. 

Recently, the ability of fi-CyD to form particles without polymers or phosphohpids has been studied. Indeed, by employing a reticulation of -CyD during the preparation process, it is possible to directly obtain microparticles (spheres and capsules) [10, 15]. On the other hand, reticulation of -CyD can also be performed to synthesize a -CD polymer, capable of forming nanospheres mixed with modified polysaccharide spontaneously [46]. 

The widely used carrier is silica gel. Researchers tend to modify the sihca gel or CD monomer first to make an arm for convenient immobilization. Immobilized CD polymers are stable, firm and the chemical structure could be adjusted. However, because of the large steric hindrance of CD molecules, the immobihzation yield is low. 

In addition, after the CD units were bridged by some functional groups, two adjacent CDs cavities were able to synergisticaUy partidpate in the inclusion and complexation of guest molecules with the suited shape and size. More stable supramolecular complexes would be formed to better analog the biological enzyme. Based on this, a series of CD polymers have been synthesized by researchers [18]. 

CDs can form inclusion complexes with iodine, which makes them candidates for iodine-sorption from nuclear waste gases. In model experiments, it was shown that the aqueous solutions containing CDs and crosslinked CD polymers were selective and effective iodine absorbers [86]. Especially the cr-CD derivatives (methylated and crosslinked) have high sorption capacity. On the basis of the results, the binding of elemental and organic iodine emitted into the air by chemical and nuclear power plants can be made effectively by immobilizing iodine vapor in aqueous CD solutions or in CD polymer gel beds. Such new sorbents can be employed in the air filtration systems (Table 8.4). 

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